242 AGRICULTURE 



where the soil contains little air, that is, where the soil 

 packs down heavily, or where the land has been poorly 

 prepared for the growth of cotton. Therefore, better cir- 

 culation of air in the soil is needed. This can be attained 

 by deep plowing, thorough cultivation, and the addition of 

 stable manure or vegetable matter. Rotation of crops is 

 necessary. Such a rotation should not include alfalfa, 

 sweet potatoes, or other plants on which this fungus can 

 live. On land where cotton root rot occurs, corn, the small 

 grains, sorghum, the true grasses, and many other similar 

 crops may be grown. 



Cotton boll rot. The boll rot is a very common disease 

 in moist seasons. It is most severe in moist bottom lands 

 where the large plants shade the ground and the bolls. 

 The careful observer will notice first upon the boll small 

 water-soaked spots, and as these spots increase in size 

 they become gray at the center and finally pink, with a 

 purple border. The pink or gray coating is evidence of 

 the abundant production of fungus spores. These spores 

 are blown about, or spread by insects, thus planting the 

 disease wherever they fall upon cotton bolls surrounded 

 by sufficient moisture and warmth to make the spores 

 develop. The boll rots and the contents are ruined. 

 Varieties differ somewhat in the extent to which they 

 take the disease. Wide spaces between rows may de- 

 crease boll rot by letting in more sunlight. 



Black rust. This is the disease that so generally 

 causes the cotton plant gradually to drop its leaves. 

 The leaves turn pale or yellow, and then blacken and 

 die. Black rust is not started by germs. After a plant 



